{"id":"CVE-2026-102820","revision":null,"records":[{"revision":"8288c01d3cd54c1e9ba322c135a4e5bf","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-102820","aliases":[],"title":"pageant: Out-of-bounds read / oversized allocation in `pageant` MemoryMap::read via a malicious Pageant agent (Windows)","description":"pageant provides a [PageantStream] type that implements [AsyncRead] and [AsyncWrite] traits and can be used to talk to a running Pageant instance. Prior to pageant 0.2.3, the Windows pageant crate's pageant/src/wmmessage.rs MemoryMap::read function trusts a peer-controlled u32 response length supplied through the 8192-byte Pageant shared-memory mapping reached by AgentClient::connect_pageant. A local process that impersonates the Pageant window can make query_pageant_direct allocate up to approximately 4 GiB and copy beyond the mapped view, reliably crashing a russh client and conditionally exposing adjacent committed memory. This issue is fixed in pageant 0.2.3.","state":0,"publishedAt":"2026-09-29T18:18:43.297+00:00","modifiedAt":"2026-09-30T20:11:08.453+00:00","affected":[{"ecosystem":"Vendor product","name":"russh","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Eugeny\",\n                    \"product\": \"russh\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 0.63.2\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"pageant","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"rust\",\n                    \"product\": \"pageant\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 0.2.3\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":6.2,"severity":"MEDIUM"}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-g4mp-vgx3-xrvm","https://github.com/Eugeny/russh/commit/5d566989ebabfdebfe6b33243d31765a0812260b","https://github.com/Eugeny/russh/releases/tag/v0.63.2"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-102820","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-102820","identifiers":["CVE-2026-102820"]},"retained":false,"historicalAffected":[]},{"revision":"4294eb19f75f440f9593e72e85c88b0b","observedAt":"2026-11-11T05:29:25.306+00:00","statement":{"source":"euvd","id":"EUVD-2026-89203","aliases":["CVE-2026-102820","GHSA-g4mp-vgx3-xrvm"],"title":"pageant provides a [PageantStream] type that implements [AsyncRead] and [AsyncWrite] traits and can be used to talk to a running Pageant instance. Prior to pageant 0.2.3, the Windows pageant crate's pageant/src/wmmessage.rs MemoryMap::read …","description":"pageant provides a [PageantStream] type that implements [AsyncRead] and [AsyncWrite] traits and can be used to talk to a running Pageant instance. Prior to pageant 0.2.3, the Windows pageant crate's pageant/src/wmmessage.rs MemoryMap::read function trusts a peer-controlled u32 response length supplied through the 8192-byte Pageant shared-memory mapping reached by AgentClient::connect_pageant. A local process that impersonates the Pageant window can make query_pageant_direct allocate up to approximately 4 GiB and copy beyond the mapped view, reliably crashing a russh client and conditionally exposing adjacent committed memory. This issue is fixed in pageant 0.2.3.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":6.2,"severity":null}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-g4mp-vgx3-xrvm","https://github.com/Eugeny/russh/commit/5d566989ebabfdebfe6b33243d31765a0812260b","https://github.com/Eugeny/russh/releases/tag/v0.63.2"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-89203","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Sep 29, 2026, 6:18:43 PM","dateUpdated":"Sep 30, 2026, 8:11:08 PM"},"relatedAdvisories":[],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-89203","identifiers":["EUVD-2026-89203","CVE-2026-102820","GHSA-g4mp-vgx3-xrvm"]},"retained":false,"historicalAffected":[]},{"revision":"4062dc47d2104baebcd3889a93cf8b80","observedAt":"2026-10-25T04:17:26.915+00:00","statement":{"source":"nvd","id":"CVE-2026-102820","aliases":[],"title":"pageant provides a [PageantStream] type that implements [AsyncRead] and [AsyncWrite] traits and can be used to talk to a running Pageant instance. Prior to pageant 0.2.3, the Windows pageant crate's pageant/src/wmmessage.rs MemoryMap::read …","description":"pageant provides a [PageantStream] type that implements [AsyncRead] and [AsyncWrite] traits and can be used to talk to a running Pageant instance. Prior to pageant 0.2.3, the Windows pageant crate's pageant/src/wmmessage.rs MemoryMap::read function trusts a peer-controlled u32 response length supplied through the 8192-byte Pageant shared-memory mapping reached by AgentClient::connect_pageant. A local process that impersonates the Pageant window can make query_pageant_direct allocate up to approximately 4 GiB and copy beyond the mapped view, reliably crashing a russh client and conditionally exposing adjacent committed memory. This issue is fixed in pageant 0.2.3.","state":0,"publishedAt":"2026-09-29T19:17:23.82+00:00","modifiedAt":"2026-09-30T21:17:05.797+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":6.2,"severity":"MEDIUM"}],"references":["https://github.com/Eugeny/russh/commit/5d566989ebabfdebfe6b33243d31765a0812260b","https://github.com/Eugeny/russh/releases/tag/v0.63.2","https://github.com/Eugeny/russh/security/advisories/GHSA-g4mp-vgx3-xrvm"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-102820","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Deferred","weaknesses":["CWE-125","CWE-789"],"productCriteria":[],"sourceDates":{"published":"2026-09-29T19:17:23.820","lastModified":"2026-09-30T21:17:05.797"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-102820","identifiers":["CVE-2026-102820"]},"retained":false,"historicalAffected":[]},{"revision":"2642c74e99d545b2a7064c9dc6010cac","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"GHSA-g4mp-vgx3-xrvm","aliases":["CVE-2026-102820"],"title":"pageant: Out-of-bounds read / oversized allocation in `pageant` MemoryMap::read via a malicious Pageant agent (Windows)","description":"## Summary\n\n`MemoryMap::read` in the `pageant` crate (part of the russh workspace, used by\nrussh's SSH-agent client on Windows via `AgentClient::connect_pageant`) copies a\n**peer-controlled** number of bytes out of an 8192-byte shared-memory view with\n**no bounds check** — unlike the sibling `MemoryMap::write`, which correctly\nrejects oversize access with `Error::Overflow`. The byte count comes straight\nfrom a `u32` length prefix that the responding \"Pageant\" process writes into the\nshared mapping. A malicious local process that answers as the Pageant agent can\ntherefore cause:\n\n- an **out-of-bounds read** past the 8 KiB view (access violation → process\n  crash; or disclosure of adjacent process memory if the following page is\n  committed)\n- an allocation of up to **~4 GiB** from a single `u32` (`vec![0; n]`).\n\nThis was reproduced **end-to-end against the real, unmodified `pageant` crate**\n(not a model) on `x86_64-pc-windows-gnu` under Wine; see \"Proof of concept\".\n\n## Impact\n\n- **Availability / DoS (reliable).** `MemoryMap::read(size)` walks off the end of\n  the 8192-byte view and faults on the next, unmapped page — an\n  `EXCEPTION_ACCESS_VIOLATION` that crashes the russh SSH client. Independently,\n  a `size` near `u32::MAX` drives a ~4 GiB `vec![0; n]` before any copy.\n- **Confidentiality (conditional).** If memory immediately after the mapped view\n  happens to be committed, `read` returns those adjacent bytes to russh as the\n  \"agent response\", which russh then parses as agent identities/signatures. This\n  arm depends on process memory layout, so it is opportunistic; the crash/alloc\n  is the deterministic outcome.\n- **Trust boundary.** russh locates the agent with\n  `FindWindowW(\"Pageant\", \"Pageant\")` and passes the shared-mapping name inside\n  the `WM_COPYDATA` `COPYDATASTRUCT`. **Any** local process can register a window\n  of class + title `\"Pageant\"`, receive that name, open the same mapping, and\n  write a hostile `size`. So an unprivileged local process impersonating Pageant\n  can attack every russh-based SSH client that uses the Pageant agent.\n\n## Affected component\n\n- `pageant/src/wmmessage.rs`\n  - `MemoryMap::read` (`:160-171`) — no bound (contrast `MemoryMap::write`\n    `:139-158`, which returns `Error::Overflow` when `pos + len > length`).\n  - `query_pageant_direct` (`:199-237`) — reads a 4-byte `u32` size from the\n    shared mapping (`:233`) and calls `map.read(size)` (`:234`) with no check\n    against `_AGENT_MAX_MSGLEN` (8192).\n- Reached from russh via `AgentClient::connect_pageant` → `PageantStream` →\n  `query_pageant_direct`.\n\nPlatform: **Windows only** (`cfg(windows)`), local attacker. Verified against\nthe `pageant` crate **v0.2.2** as shipped in russh **v0.63.1** (`d3ae702`, the\nlatest release). `read` has never had a bound in any revision\n(`git log -p -- pageant/src/wmmessage.rs`).\n\n## Details\n\n```rust\nfn write(&mut self, data: &[u8]) -> Result<(), Error> {\n    if self.pos + data.len() > self.length {      // :140  BOUND PRESENT\n        return Err(Error::Overflow);\n    }\n    ... copy_nonoverlapping(&data[0], view+pos, data.len()) ...\n}\n\nfn read(&mut self, n: usize) -> Vec<u8> {         // :160  NO BOUND\n    let out = vec![0; n];                         // n up to 0xFFFF_FFFF (CWE-789)\n    unsafe {\n        std::ptr::copy_nonoverlapping(\n            self.view.Value.add(self.pos) as *const u8,   // view is length==8192\n            out.as_ptr() as *mut u8,\n            n,                                    // reads n bytes, may run past the view (CWE-125)\n        );\n    }\n    self.pos += n;\n    out\n}\n```\n\n`query_pageant_direct` creates the mapping at `_AGENT_MAX_MSGLEN = 8192`, writes\nthe request, sends the `WM_COPYDATA`, then reads the response the peer wrote:\n\n```rust\nmap.seek(0);\nlet mut buf = map.read(4);\nlet size = u32::from_be_bytes([buf[0],buf[1],buf[2],buf[3]]) as usize; // :233 peer-controlled\nbuf.extend(map.read(size));                                            // :234 unbounded\n```\n\nNothing checks `4 + size <= 8192`, so `map.read(size)` runs past the 8 KiB view.\n\n## Proof of concept\n\nBecause the bug is Windows-only (`WM_COPYDATA` + `MapViewOfFile`), the PoC is a\nWindows cross-build (`x86_64-pc-windows-gnu`) driven under **Wine**, entirely\ninside a Linux container. It exercises the **real, unmodified** crate: the PoC\ntakes a path dependency on `pageant` and calls\n`pageant::wmmessage::query_pageant_direct`, exactly what\n`AgentClient::connect_pageant` uses. A second thread impersonates Pageant\n(registers the window class + title `\"Pageant\"`) and, on `WM_COPYDATA`, opens\nthe shared mapping russh created and writes an attacker-chosen 4-byte\nbig-endian length.\n\n`poc/run.sh` builds and runs it. Full log in `results/e2e-wine-run.log`:\n\n```\n======== LEG 1 — ATTACK: fake agent reports length 0x00080000 (512 KiB) >> 8192-byte view ========\n[attacker] impersonating Pageant window is up (class+title \"Pageant\")\n[victim ] calling pageant::wmmessage::query_pageant_direct() over the 8192-byte view ...\n[attacker] WM_COPYDATA received; shared mapping = \"PageantRequestpoc\"\n[attacker] wrote hostile response length = 524288 (0x00080000) into the 8192-byte view\nwine: Unhandled page fault on read access to 0000000002092000 at address 00000002282CFDC4 ...\nWINE-EXIT=5\n\n======== LEG 2 — CONTROL: fake agent reports length 0x00000010 (16 B), in-bounds ========\n[victim ] returned 20 bytes — request+response fit inside the 8192-byte view (in-bounds control); no fault\nWINE-EXIT=0\n```\n\n- **LEG 1 (attack)**: an oversized `size` makes `MemoryMap::read` read past the\n  8192-byte view; Wine reports an unhandled page fault at a page-aligned address\n  (`0x…2092000`) — the out-of-bounds read as an access violation (crash). Exit\n  code 5 = `STATUS_ACCESS_VIOLATION`.\n- **LEG 2 (control)**: an in-bounds `size` returns cleanly. Same code path; the\n  only difference is whether the peer's length exceeds the view — isolating the\n  missing bound.\n\n**Fix validation.** With `patch/pageant-read-bound.patch` applied and the PoC\nrebuilt against the patched crate, the identical attack input is rejected\n(`results/patched-wine-run.log`):\n\n```\n[attacker] wrote hostile response length = 524288 (0x00080000) into the 8192-byte view\n[victim ] query_pageant_direct error: Overflow\nWINE-EXIT=0\n```\n\nNo fault; the read is refused at the bound, exactly as `write` already refuses\noversize writes. (A pure-logic Linux model of the same control flow is also\nincluded as `poc/pageant_read_oob_demo.rs` / `results/logic-demo-run.log`.)\n\n## Remediation\n\nMirror `write`'s guard in `read` and validate the response length before\nallocating/copying. `patch/pageant-read-bound.patch`:\n\n- `MemoryMap::read(n)` returns `Result<Vec<u8>, Error>` and returns\n  `Error::Overflow` when `self.pos + n > self.length`;\n- `query_pageant_direct` propagates that `Result` and additionally rejects\n  `size > _AGENT_MAX_MSGLEN - 4` before `map.read(size)`.","state":0,"publishedAt":"2026-09-30T23:41:02+00:00","modifiedAt":"2026-10-01T00:00:04.6800173+00:00","affected":[{"ecosystem":"crates.io","name":"pageant","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"0.2.3"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-g4mp-vgx3-xrvm","https://nvd.nist.gov/vuln/detail/CVE-2026-102820","https://github.com/Eugeny/russh/commit/5d566989ebabfdebfe6b33243d31765a0812260b","https://github.com/Eugeny/russh","https://github.com/Eugeny/russh/releases/tag/v0.63.2"],"sourceUrl":"https://github.com/advisories/GHSA-g4mp-vgx3-xrvm","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-g4mp-vgx3-xrvm","identifiers":["GHSA-g4mp-vgx3-xrvm","CVE-2026-102820"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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