CVE-2021-41773

high KEV

Published 2021-11-03 · Modified 2021-11-03

💬 Discuss on Community ✚ Propose mitigation

CVSS v3

—

CVSS v4 NEW

—

not yet in upstream

VIR risk

10.0

Description

A flaw was found in a change made to path normalization in Apache HTTP Server 2.4.49. An attacker could use a path traversal attack to map URLs to files outside the directories configured by Alias-like directives. If files outside of these directories are not protected by the usual default configuration "require all denied", these requests can succeed. If CGI scripts are also enabled for these aliased pathes, this could allow for remote code execution. This issue is known to be exploited in the wild. This issue only affects Apache 2.4.49 and not earlier versions. The fix in Apache HTTP Server 2.4.50 was found to be incomplete, see CVE-2021-42013.

CISA KEV

Vendor: Apache
Product: HTTP Server
Due date: 2021-11-17

Predictions

Exploit likelihood

99%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

Exploits

Public proof-of-concept code below. AS-IS, for defenders and authorised testing only.

Exploit-DB

EDB-50383 webapps multiple verified

Lucas Souza · 2021-10-06

Apache HTTP Server 2.4.49 - Path Traversal & Remote Code Execution (RCE)

Source code queued for fetch — refresh in a moment.

EDB-50512 webapps multiple verified

Valentin Lobstein · 2021-11-11

Apache HTTP Server 2.4.50 - Remote Code Execution (RCE) (3)

Source code queued for fetch — refresh in a moment.

Metasploit modules

exploit_multi/http/apache_normalize_path_rce rank 600

Apache 2.4.49/2.4.50 Traversal RCE

Source code queued for fetch — refresh in a moment.

auxiliary_scanner/http/apache_normalize_path rank 300

Apache 2.4.49/2.4.50 Traversal RCE scanner

Source fetch failed: fetch_error — view the original via the link above.

OS impact

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

Arch Fixed 1 release

Version	Status	Fixed in
—	Fixed	`2.4.50-1`

Debian Fixed 5 releases

Version	Status	Fixed in
trixie	Fixed	`2.4.50-1`
sid	Fixed	`2.4.50-1`
forky	Fixed	`2.4.50-1`
bullseye	Fixed	`0`
bookworm	Fixed	`2.4.50-1`

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.