Unrated

Unauthenticated DoS in vouch-proxy multipart cookie reassembly

IdentifiersCVE-2026-55149CWE-770

CVE-2026-55149 is an unauthenticated remote denial-of-service vulnerability in vouch-proxy caused by unbounded memory allocation during multipart cookie reassembly. The flaw affects logic that parses multipart cookie names on authentication-related endpoints such as /validate and /_external-auth-:id. An attacker can supply a crafted multipart cookie name containing an invalid or excessively large part count, which is then used directly in allocation for cookie-part storage without adequate bounds checking or format validation. This can trigger massive memory allocation and cause the process to terminate from out-of-memory conditions.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows a remote unauthenticated attacker to crash the vouch-proxy service with a single crafted request, resulting in immediate denial of service. Repeated requests can keep the service unavailable. Depending on deployment architecture and reverse-proxy behavior, this outage may also disrupt access to downstream applications protected by vouch-proxy, and in some fail-open configurations could weaken authentication enforcement during service failure.

Mitigation

If you can’t patch tonight, do this now.

Apply strict server-side validation to multipart cookie name parsing and enforce a hard upper bound on the number of cookie parts accepted for reassembly. Reject malformed values, including invalid formats and zero, negative, or excessively large part counts, rather than using attacker-controlled counts in memory allocation. As an operational safeguard, place the service behind request filtering or a reverse proxy capable of blocking malformed cookie input and use resource limits and monitoring to reduce denial-of-service impact.

Remediation

Patch, then assume compromise.

Upgrade vouch-proxy to version 0.48.0 or later, which addresses the vulnerable multipart cookie parsing behavior. If upgrading is not immediately possible, modify the affected parsing logic to enforce strict bounds on multipart cookie part counts and reject malformed multipart cookie names before any allocation occurs.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

VouchVouch-Proxyapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

No public activity tracked yet. Mallory keeps watching.

0 SOURCESView more in app

No public activity observed for this vulnerability.

What this page doesn’t show

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

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Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity