How severe is CVE-2026-45057?

CVE-2026-45057 has a CVSS score of 4.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-45057?

CVE-2026-45057 affects the following packages: matrix-sdk-ui (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2026-45057?

Update matrix-sdk-ui to 0.16.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45057 is resolved across your whole dependency graph.

How do I detect CVE-2026-45057 in my crates.io dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for matrix-sdk-ui, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-45057 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-45057 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-45057 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-45057?

CVE-2026-45057 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 13th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-45057?

CVE-2026-45057 is classified as CWE-345 (CWE-345). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-45057 published, and has it been updated?

CVE-2026-45057 was published on September 11, 2026 and was last updated on October 2, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🦀

🦀 crates.io

Not in CISA KEV

MEDIUM severity

CVE-2026-45057 — matrix-sdk-ui

MEDIUMFix: matrix-org/matrix-rust-sdk#6454

CVE-2026-45057 is a medium-severity (CVSS 4.9) CWE-345 vulnerability in matrix-sdk-ui. A fix is available for matrix-sdk-ui — see the affected versions and patch details below.

matrix-sdk-ui: Incomplete edit validation

Also known asGHSA-h97m-27fx-42rxRUSTSEC-2026-0158

Published

Sep 11, 2026

Updated

Oct 2, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 13, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45057.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs13th percentile — riskier than 13% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-45057 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 390,400 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🦀matrix-sdk-ui

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.

Description

Impact

The message edit validation logic in the matrix-sdk-ui crate before 0.16.1 is missing a check: when replacing an encrypted event, the replacement event itself is not required to be encrypted. This enables a malicious homeserver administrator (or an actor with equivalent power) to impersonate or spoof messages as if they were sent by a victim user.

Patches

matrix-sdk-ui 0.16.1 fixes the message edit validation logic to align with the algorithm for replacement events¹ described in the Matrix specification.

Workarounds

N/A

References

Pull request: https://github.com/matrix-org/matrix-rust-sdk/pull/6454

For more information

If you have any questions or comments about this advisory, please email us at security at matrix.org.

Footnotes

https://spec.matrix.org/unstable/client-server-api/#validity-of-replacement-events ↩

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`matrix-sdk-ui`	all versions	0.16.1`cargo update -p matrix-sdk-ui --precise 0.16.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for matrix-sdk-ui, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update matrix-sdk-ui to 0.16.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45057 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact The message edit validation logic in the `matrix-sdk-ui` crate before 0.16.1 is missing a check: when replacing an encrypted event, the replacement event itself is not required to be encrypted. This enables a malicious homeserver administrator (or an actor with equivalent power) to impersonate or spoof messages as if they were sent by a victim user. ### Patches `matrix-sdk-ui` 0.16.1 fixes the message edit validation logic to align with the algorithm for replacement events[^1] described in the Matrix specification. ### Workarounds N/A ### References * Pull request: https://githu