7.5

CVE-2021-33193: Request splitting via HTTP/2 method injection and mod_proxy

Analyzed
AliasesALPINE-CVE-2021-33193SUSE-SU-2021:2918-1SUSE-SU-2021:2954-1
Published 16-08-2021Last modified 03-08-2024

Vulnerability summary

CVE-2021-33193 is a high (CVSS 7.5) vulnerability in apache software foundation apache http server. EPSS estimates a 46.18% chance of exploitation in the next 30 days, higher than 98.8% of scored vulnerabilities. 1 public exploit is recorded.

Priority
Prioritisepublic exploit

Public exploit (reference, Date unknown)

Source freshness unavailable

How is this decided?
CVSS score
7.5/10
010
High · v3.1 (NVD)
EPSS score
46.18%
0%100%
High · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits1reference

Advisory lineage

Upstream 0 · Downstream 7 · Related 2
DLA-3351-1MGASA-2021-0439RHSA-2022:1915RHSA-2022:6753RHSA-2022:7143SUSE-SU-2021:3335-1

Timeline

  1. 16-08-2021
    PublishedVulnerability first disclosed.
  2. 03-08-2024
    Last modifiedVulnerability information updated.

Description

A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.

CVSS metrics

5 scores · 4 sources · 2 versions

EPSS trend

Probability

46.18%

Chance of exploitation in the next 30 days

Percentile

99%

Versus all other CVEs

30-day change

No change 0.00 pp

From 46.18% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

1 found
  • referenceUnverified

    Exploit Reference (portswigger.net)

    Maturity: unknown

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Suse8 products
  • apache2&distro=SUSE Linux Enterprise Module for Basesystem 15 SP2< 2.4.43-3.25.1
  • apache2&distro=SUSE Linux Enterprise Module for Basesystem 15 SP3< 2.4.43-3.25.1
  • apache2&distro=SUSE Linux Enterprise Module for Package Hub 15 SP3< 2.4.43-3.25.1
  • apache2&distro=SUSE Linux Enterprise Module for Server Applications 15 SP2< 2.4.43-3.25.1
  • apache2&distro=SUSE Linux Enterprise Module for Server Applications 15 SP3< 2.4.43-3.25.1
Debian2 products
Opensuse2 products
  • apache2&distro=openSUSE Leap 15.2< 2.4.43-lp152.2.18.1
  • apache2&distro=openSUSE Leap 15.3< 2.4.43-3.25.1
Oracle2 products
Alpine1 product
  • apache2< 2.4.49-r0
Apache1 product
Apache software foundation1 product
Fedoraproject1 product
Tenable1 product
Ubuntu1 product
  • apache2< 2.4.29-1ubuntu4.17 | < 2.4.41-4ubuntu3.5

10 vendors · 20 products

References

25 links
Show all 25 references