rustls webpki 0.101.0 before 0.103.12 Name Constraint Bypass

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rustls-webpki (the Rust webpki fork used by rustls) versions >= 0.101.0 and prior to 0.103.12 and 0.104.0-alpha.6 incorrectly accepted permitted-subtree DNS name constraints for certificates asserting a wildcard name. For example, a name constraint of accept.example.com was treated as satisfied by a certificate for *.example.com, which could feasibly assert reject.example.com — a name outside the permitted subtree. Because name constraints are restrictions applied to otherwise properly issued certificates, the issue is only reachable after signature verification succeeds and requires a misissued wildcard certificate to exploit.

Source published

18 Sep 2026 13:20:11 UTC

Source modified

18 Sep 2026 17:49:52 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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CVSS 4.0 · 2.1 CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS 3.1 · 2.2 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N

rustls-webpki (the Rust webpki fork used by rustls) versions >= 0.101.0 and prior to 0.103.12 and 0.104.0-alpha.6 incorrectly accepted permitted-subtree DNS name constraints for certificates asserting a wildcard name. For example, a name constraint of accept.example.com was treated as satisfied by a certificate for *.example.com, which could feasibly assert reject.example.com — a name outside the permitted subtree. Because name constraints are restrictions applied to otherwise properly issued certificates, the issue is only reachable after signature verification succeeds and requires a misissued wildcard certificate to exploit.

Source published

Sep 18, 2026, 1:20:11 PM (timezone not stated)

Source modified

Sep 18, 2026, 5:49:52 PM (timezone not stated)

Saved here

11 Nov 2026 17:05:42 UTC

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EUVD CVSS 4.0 · 2.1 CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

rustls-webpki (the Rust webpki fork used by rustls) versions >= 0.101.0 and prior to 0.103.12 and 0.104.0-alpha.6 incorrectly accepted permitted-subtree DNS name constraints for certificates asserting a wildcard name. For example, a name constraint of accept.example.com was treated as satisfied by a certificate for *.example.com, which could feasibly assert reject.example.com — a name outside the permitted subtree. Because name constraints are restrictions applied to otherwise properly issued certificates, the issue is only reachable after signature verification succeeds and requires a misissued wildcard certificate to exploit.

Source published

18 Sep 2026 14:19:11 UTC

Source modified

22 Sep 2026 20:25:55 UTC

Saved here

25 Oct 2026 16:19:28 UTC

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NIST NVD usage terms; underlying source attribution retained

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CVSS 4.0 · [email protected] · Secondary · 2.1 CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Secondary · 2.2 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N

Permitted subtree name constraints for DNS names were accepted for certificates asserting a wildcard name. This was incorrect because, given a name constraint of `accept.example.com`, `*.example.com` could feasibly allow a name of `reject.example.com` which is outside the constraint. This is very similar to [CVE-2025-61727](https://go.dev/issue/76442). Since name constraints are restrictions on otherwise properly-issued certificates, this bug is reachable only after signature verification and requires misissuance to exploit.

Source published

16 Apr 2026 21:17:12 UTC

Source modified

19 Sep 2026 03:55:49 UTC

Saved here

24 Oct 2026 13:19:54 UTC

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GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N

Publisher rating · LOW

Permitted subtree name constraints for DNS names were accepted for certificates asserting a wildcard name. This was incorrect because, given a name constraint of `accept.example.com`, `*.example.com` could feasibly allow a name of `reject.example.com` which is outside the constraint. This is very similar to [CVE-2025-61727](https://go.dev/issue/76442). Since name constraints are restrictions on otherwise properly-issued certificates, this bug is reachable only after signature verification and requires misissuance to exploit. This vulnerability is identified as [GHSA-xgp8-3hg3-c2mh](https://github.com/rustls/webpki/security/advisories/GHSA-xgp8-3hg3-c2mh). Thank you to [@1seal](https://github.com/1seal) for the report.

Source published

14 Apr 2026 12:00:00 UTC

Source modified

19 Sep 2026 08:42:27 UTC

Saved here

24 Oct 2026 13:19:54 UTC

Source terms

OSV · upstream source license applies

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