Summary
Moov signedxml: Unauthenticated denial of service in exclusive XML canonicalization
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.
Credit
Reported by Shuji Ohira (@shuji-oh).
Impact
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2026-113729 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.4.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
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!
Frequently Asked Questions
- What is CVE-2026-113729? CVE-2026-113729 is a high-severity uncontrolled resource consumption vulnerability in github.com/moov-io/signedxml (go), affecting versions <= 1.4.0. It is fixed in 1.4.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2026-113729? CVE-2026-113729 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/moov-io/signedxml are affected by CVE-2026-113729? github.com/moov-io/signedxml (go) versions <= 1.4.0 is affected.
- Is there a fix for CVE-2026-113729? Yes. CVE-2026-113729 is fixed in 1.4.1. Upgrade to this version or later.
- Is CVE-2026-113729 exploitable, and should I be worried? Whether CVE-2026-113729 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-113729 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-113729? Upgrade
github.com/moov-io/signedxmlto 1.4.1 or later.