How severe is CVE-2026-55406?

No CVSS score has been assigned to CVE-2026-55406 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-55406?

CVE-2026-55406 affects the following packages: buffa (crates.io). Ecosystems affected: crates.io.

How do I fix CVE-2026-55406?

Update buffa to 0.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55406 is resolved across your whole dependency graph.

How do I detect CVE-2026-55406 in my crates.io dependencies?

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

How do I mitigate CVE-2026-55406 if there is no patch (or I can't update yet)?

Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Is CVE-2026-55406 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-55406 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-2026-55406?

CVE-2026-55406 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 8th 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-2026-55406?

CVE-2026-55406 is classified as Information Exposure (CWE-200), Use After Free (CWE-416). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-55406 published, and has it been updated?

CVE-2026-55406 was published on July 16, 2026 and was last updated on August 12, 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

CVE-2026-55406 — buffa

Fix: anthropics/buffa@7dcf50a

CVE-2026-55406 is a Information Exposure vulnerability in buffa. A fix is available for buffa — see the affected versions and patch details below.

Buffa: Use-After-Free in OwnedView via Unsound 'static Lifetime Promotion in Deref

Also known asGHSA-9pwq-gcrx-wghh

Published

Jul 16, 2026

Updated

Aug 12, 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-2026-55406.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs8th percentile — riskier than 8% of all scored CVEsHighest risk

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

Real-World Exposure

1 pkg affected

🦀buffa

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

A soundness bug in buffa's OwnedView<V> allowed safe Rust code to trigger a use-after-free. The OwnedView::decode constructor transmuted a borrowed slice to &'static [u8], and the Deref implementation exposed the promoted 'static lifetime on borrowed view fields (such as &'static str and &'static [u8]) to callers. Because these references appeared to be 'static, the borrow checker permitted them to outlive the OwnedView; once the OwnedView was dropped and its backing buffer freed, those references became dangling, enabling memory corruption, information disclosure of freed heap contents, and cross-thread misuse — all without any unsafe code in the calling application. Users are advised to update to the latest patched version of buffa.

Thank you to hackerone.com/suul for reporting this issue.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`buffa`	all versions	0.7.0`cargo update -p buffa --precise 0.7.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for buffa, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update buffa to 0.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55406 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Frequently Asked Questions

A soundness bug in `buffa`'s `OwnedView<V>` allowed safe Rust code to trigger a use-after-free. The `OwnedView::decode` constructor transmuted a borrowed slice to `&'static [u8]`, and the `Deref` implementation exposed the promoted `'static` lifetime on borrowed view fields (such as `&'static str` and `&'static [u8]`) to callers. Because these references appeared to be `'static`, the borrow checker permitted them to outlive the `OwnedView`; once the `OwnedView` was dropped and its backing buffer freed, those references became dangling, enabling memory corruption, information disclosure of free

O3 Security · Impact-Aware SCA

Is CVE-2026-55406 in your dependencies?

Find it across crates.io, including transitive dependencies.

Scan my dependencies How O3 SCA works