Moov signedxml: Unauthenticated denial of service in exclusive XML canonicalization

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Moov signedxml is a pure Go library for processing signed XML documents. Prior to 1.4.1, ExclusiveCanonicalization in exclusivecanonicalization.go copies the complete accumulated namespace map at every nested element before reference digest or signature checks. Attacker-controlled XML containing deeply nested elements with many unused namespace declarations causes quadratic allocation growth with depth and linear growth with prefixes per level, allowing a comparatively small document to consume multiple gigabytes of memory and terminate the process. The condition is reachable through ValidateReferences without a valid signature, matching certificate, or prior authentication, and it does not bypass signature verification. This issue is fixed in version 1.4.1.

Source published

20 Oct 2026 21:17:55 UTC

Source modified

27 Oct 2026 11:07:28 UTC

Observed here

27 Oct 2026 13:09:22 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Moov signedxml is a pure Go library for processing signed XML documents. Prior to 1.4.1, ExclusiveCanonicalization in exclusivecanonicalization.go copies the complete accumulated namespace map at every nested element before reference digest or signature checks. Attacker-controlled XML containing deeply nested elements with many unused namespace declarations causes quadratic allocation growth with depth and linear growth with prefixes per level, allowing a comparatively small document to consume multiple gigabytes of memory and terminate the process. The condition is reachable through ValidateReferences without a valid signature, matching certificate, or prior authentication, and it does not bypass signature verification. This issue is fixed in version 1.4.1.

Source published

Oct 20, 2026, 9:17:55 PM (timezone not stated)

Source modified

Oct 27, 2026, 11:07:28 AM (timezone not stated)

Observed here

1 Nov 2026 02:13:54 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Moov signedxml is a pure Go library for processing signed XML documents. Prior to 1.4.1, ExclusiveCanonicalization in exclusivecanonicalization.go copies the complete accumulated namespace map at every nested element before reference digest or signature checks. Attacker-controlled XML containing deeply nested elements with many unused namespace declarations causes quadratic allocation growth with depth and linear growth with prefixes per level, allowing a comparatively small document to consume multiple gigabytes of memory and terminate the process. The condition is reachable through ValidateReferences without a valid signature, matching certificate, or prior authentication, and it does not bypass signature verification. This issue is fixed in version 1.4.1.

Source published

20 Oct 2026 22:19:29 UTC

Source modified

27 Oct 2026 12:17:06 UTC

Observed here

29 Oct 2026 06:48:04 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exclusive XML canonicalization (`http://www.w3.org/2001/10/xml-exc-c14n#`) in `github.com/moov-io/signedxml` copied the entire accumulated namespace map at every node during `ValidateReferences()`, before any reference digest or signature check. For a chain of nested elements that each declare many unused namespace prefixes, that produced **O(m × depth²)** time and peak memory (`m` = prefixes per level). `beevik/etree` caps tree depth (~1024), but `m` is unbounded, so a small attacker-controlled document (on the order of 1 MB) could drive multi-gigabyte allocations and OOM the process. No valid signature, matching certificate, or authentication is required. This is the library’s core path for SAML / WS-Federation service providers, which canonicalize attacker-supplied XML prior to authentication. ### Affected - Package: `github.com/moov-io/signedxml` - Function: `ExclusiveCanonicalization` (`exclusivecanonicalization.go`) - Verified: **v1.4.0** and current default branch (commit `d79064a`). Earlier v1.2.x–v1.3.x releases are likely affected. ### Remediation Do not copy the whole namespace map per node. Maintain a single scope and push/pop only the prefixes introduced at each element. Replace linear prefix-in-scope scans with set lookups. Impose a defensive cap on in-scope namespace declarations and return an error rather than allocating unbounded memory. From @shuji-oh ``` Thanks for the fix — I re-ran my PoC against this branch and confirmed the memory blowup is gone. Before (main) -- Doubling depth each time (m=10 fixed): allocated grows ~4x each time ≈ O(depth^2) -- depth=250 m=10 payload= 0.07MB allocated= 45MB depth=500 m=10 payload= 0.14MB allocated= 179MB depth=1000 m=10 payload= 0.27MB allocated= 711MB -- Increasing m (depth=1000 fixed): allocated scales roughly linearly with m -- depth=1000 m=5 payload= 0.16MB allocated= 377MB depth=1000 m=100 payload= 2.57MB allocated= 6278MB After (fix/exc-c14n-namespace-dos) -- Doubling depth each time (m=10 fixed): allocated grows ~4x each time ≈ O(depth^2) -- depth=250 m=10 payload= 0.07MB allocated= 2MB depth=500 m=10 payload= 0.14MB allocated= 4MB depth=1000 m=10 payload= 0.27MB allocated= 7MB -- Increasing m (depth=1000 fixed): allocated scales roughly linearly with m -- depth=1000 m=5 payload= 0.16MB allocated= 4MB depth=1000 m=100 payload= 2.57MB allocated= 47MB That's roughly a 100–130x reduction in peak allocation for the same payload sizes, and no OOM in any of my runs. This looks like it resolves the issue — thanks for the quick fix! ``` ### Credit Reported by Shuji Ohira ([@shuji-oh](https://github.com/shuji-oh)).

Source published

21 Oct 2026 16:27:55 UTC

Source modified

21 Oct 2026 16:45:04 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

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

Publisher rating · HIGH