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Proxygen CVE-2025-55181

| EUVDEUVD-2025-200372 MEDIUM
Excessive Iteration (CWE-834)
2025-12-02 cve-assign@fb.com
5.3
CVSS 3.1 · Vendor: fb
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Excessive iteration
Impact

CVSS 5.3. EPSS 0.1%. Vendor patch available.

Exploit ScenarioDerived

An attacker could exploit this vulnerability in the affected application to compromise the security of affected deployments, potentially impacting confidentiality, integrity, or availability.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 15, 2026

CVE-2025-55181 is a security vulnerability (CVSS 5.3). Remediation should follow standard vulnerability management procedures. Vendor patch is available.

Earlier versions of this analysis (1)
v1 Mar 15, 2026 - 14:04 CVSS 5.3

Sending an HTTP request/response body with greater than 2^31 bytes triggers an infinite loop in proxygen::coro::HTTPQuicCoroSession which blocks the backing event loop and unconditionally appends data

RemediationAI

Apply the vendor-supplied patch immediately.

Affected VersionsENISA

Proxygen v2025.08.25.00 ≤v2025.12.01.00

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Vulnerability type not specified by vendor.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (fb) PRIMARY 5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Primary rating from Vendor (fb) · only source for this CVE.

CVSS VectorVendor: fb

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

Lifecycle Timeline

2
Patch released
Mar 15, 2026 - 14:04 nvd
Patch available
CVE Published
Dec 02, 2025 - 22:16 nvd
MEDIUM 5.3

DescriptionCVE.org

Sending an HTTP request/response body with greater than 2^31 bytes triggers an infinite loop in proxygen::coro::HTTPQuicCoroSession which blocks the backing event loop and unconditionally appends data to a std::vector per-loop iteration. This issue leads to unbounded memory growth and eventually causes the process to run out of memory.

Executive ViewAI

Why It Matters

CVE-2025-55181 presents moderate security risk rated CVSS 5.3. Exploitation could compromise the security of affected deployments. A patch is available and should be applied during regular vulnerability management.

Business Impact: Low
Compensating Controls

Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.

Threat Intelligence Overview

EPSS Score
0.1%
Top 81% exploitable
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.1%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact
Low

Priority Score

26
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +26
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

CVE-2023-44487 HIGH POC
7.5 Oct 10

Denial of service against HTTP/2 server implementations allows remote unauthenticated attackers to exhaust server resour

CVE-2015-7264 CRITICAL
9.8 Apr 10

The SPDY/2 codec in Facebook Proxygen before 2015-11-09 truncates a certain field to two bytes, which allows hijacking a

CVE-2020-1897 CRITICAL
9.8 May 18

A use-after-free is possible due to an error in lifetime management in the request adaptor when a malicious client invok

CVE-2019-11940 CRITICAL
9.8 Dec 04

In the course of decompressing HPACK inside the HTTP2 protocol, an unexpected sequence of header table resize operations

CVE-2019-11921 CRITICAL
9.8 Jul 25

An out of bounds write is possible via a specially crafted packet in certain configurations of Proxygen due to improper

CVE-2015-7265 HIGH
7.5 Apr 10

Facebook Proxygen before 2015-11-09 mismanages HTTPMessage.request state, which allows remote attackers to conduct hijac

CVE-2015-7263 HIGH
7.5 Apr 10

The SPDY/2 codec in Facebook Proxygen before 2015-11-09 allows remote attackers to conduct hijacking attacks and bypass

CVE-2026-91096 HIGH
7.5 Sep 28

Use-after-free in Meta's Proxygen HTTP library (v2024.10.28.00 through v2026.09.28.00) lets remote, unauthenticated atta

CVE-2021-24029 HIGH
7.5 Mar 15

A packet of death scenario is possible in mvfst via a specially crafted message during a QUIC session, which causes a cr

CVE-2018-6347 HIGH
7.5 Dec 31

An issue in the Proxygen handling of HTTP2 parsing of headers/trailers can lead to a denial-of-service attack. Rated hig

CVE-2018-6346 HIGH
7.5 Dec 31

A potential denial-of-service issue in the Proxygen handling of invalid HTTP2 priority settings (specifically a circular

CVE-2018-6343 HIGH
7.5 Dec 31

Proxygen fails to validate that a secondary auth manager is set before dereferencing it. Rated high severity (CVSS 7.5),

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