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ASP.NET Security Feature Bypass Vulnerability

Not in CISA KEVPublic exploit codeCVE-2025-55315CWE-444

Not confirmed exploited. 1 of 8 rule sources name it.

Edge rules
1/8
Our test
No exploit yet
CVSS
9.9
EPSS
66.5% Top 0.7%
Posts, 14d
02026-10-21: 0 posts2026-10-22: 0 posts2026-10-23: 0 posts2026-10-24: 0 posts2026-10-25: 0 posts2026-10-26: 0 posts2026-10-27: 0 posts2026-10-28: 0 posts2026-10-29: 0 posts2026-10-30: 0 posts2026-10-31: 0 posts2026-11-01: 0 posts2026-11-02: 0 posts2026-11-03: 0 posts
Published
2025-10-14

Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an authorized attacker to bypass a security feature over a network.

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Ask about CVE-2025-55315: who's covered, what to patch first, how vendors compare. I cite sources and won't help with attacks.

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Severity, decoded

CVSS 3.1
Critical · 9.9 / 10

Exploitable over the network, with low privileges and no user interaction, leading to full loss of confidentiality and integrity and low impact on availability, and the impact can reach components beyond the vulnerable one.

Over the internetAny user loginNo user actionWorks reliablySpreads beyond the appSerious impact
How the score is built8 metrics
  • Attack vectorAn attacker can reach it over the internet; no access to your network needed.
    Network
  • Attack complexityNo special conditions are needed; the attack works reliably.
    Low
  • Privileges requiredThe attacker needs an ordinary user account.
    Low
  • User interactionNo one has to click or open anything; the attack works on its own.
    None
  • ScopeThe attack can spread beyond the vulnerable component to other parts of the system.
    Changed
  • Confidentiality impactAn attacker can read all data the affected component holds, or the most sensitive parts of it.
    High
  • Integrity impactAn attacker can change any data or files the affected component protects.
    High
  • Availability impactAn attacker can slow the component down or interrupt it now and then.
    Low
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L/E:U/RL:O/RC:C

Also in the vector: Exploit code maturity: Unproven · Remediation level: Official fix · Report confidence: Confirmed

CISA's assessmentSSVC, from the CVE record
ExploitationProof of concept

Public exploit code or a detailed write-up exists, but CISA has not seen attacks.

AutomatableNo

At least one step needs hands-on work, which slows mass attacks.

Technical impactTotal

A successful attack gives full control over the affected software or all of its data.

Public exploits

1 found
0 Metasploit1 Exploit-DB0 Scanner template0 GitHub PoCs

Links are to third-party code: never run it outside an isolated lab.

Timeline

  1. 2025-10-14
    CVE published
    CVE List
  2. 2025-12-03
    F5 ships a rule
    ASP.NET Core Request Smuggling
  3. 2026-04-06
    Exploit published on Exploit-DB
    ASP.net 8.0.10 - Bypass

Social

2026-10-21: 0 posts2026-10-22: 0 posts2026-10-23: 0 posts2026-10-24: 0 posts2026-10-25: 0 posts2026-10-26: 0 posts2026-10-27: 0 posts2026-10-28: 0 posts2026-10-29: 0 posts2026-10-30: 0 posts2026-10-31: 0 posts2026-11-01: 0 posts2026-11-02: 0 posts2026-11-03: 0 posts

No posts seen yet on X, Bluesky, Mastodon, Hacker News or GitHub.

Vendor statements

Quoted
CloudflareWAF Managed RulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. Each row gives the rule ID and its default action. The feed starts in January 2025, so older rules are missing.

AWSAWS WAF Managed RulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. AWS often describes a vulnerability without naming its CVE (for example "Log4j"). We count only entries that name the CVE, so AWS coverage is understated.

Microsoft AzureFront Door and Application Gateway WAF (DRS)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. The rule tables name CVEs but carry no dates, so Azure is left out of every time-to-rule figure.

Google CloudCloud Armor preconfigured WAF rulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. Google names few CVEs: the release notes start in May 2024 and the rules reference lists CVEs without dates. Its cve-canary rules are opt-in.

FastlyNext-Gen WAF virtual patchesBefore feed history

The CVE predates the oldest entry in this vendor's public feed, so a rule may exist that we cannot see.

F5Attack signatures (Distributed Cloud WAF)3 quotesRule published

First rule 2025-12-03, 50 days after the CVE was published.

2025-12-03New rule200020232Source
Added: signature 200020232 "ASP.NET Core Request Smuggling" (HTTP Parser Attack, risk High), systems: ASP.NET. References: CVE-2025-55315.
2025-12-04Updated200020232Source
Updated: signature 200020232 "Chunk-Extension Request Smuggling" (HTTP Parser Attack, risk High), systems: ASP.NET. References: CVE-2025-55315, CVE-2025-22871.
2026-09-16Updated200020232Source
Updated: signature 200020232 "Chunk-Extension Request Smuggling" (HTTP Parser Attack, risk High), systems: ASP.NET, Other Web Server, Apache Tomcat. References: CVE-2025-55315, CVE-2025-22871, CVE-2026-24880.
AkamaiApp & API Protector (Adaptive Security Engine)No public source

This vendor publishes no machine-readable rule changelog we can check.

OWASP CRSCore Rule Set (open source, used inside many WAFs)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. CRS rarely names CVEs: it relies on generic detections. Our own lab measures what it actually blocks.