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CVE-2021-21707

32
FAUCET Score

CVE-2021-21707 is a medium-severity vulnerability affecting PHP versions 7.3.x, 7.4.x, and 8.0.x, as well as products from Debian, NetApp, and Tenable. It stems from certain XML parsing functions URL-decoding filenames, potentially misinterpreting a URL-encoded NUL character as an end-of-filename marker. This could lead to unintended file access, allowing an attacker to read a different file than intended. The vulnerability has a CVSS score of 5.3, indicating a low impact on confidentiality with no integrity or availability impact, and does not require user interaction or privileges. There is no evidence of active exploitation, no public exploit code (Metasploit, Nuclei, ExploitDB), and it is not listed on the CISA KEV catalog. Community discussion and media coverage are minimal, with only one mention and one article identified.

Impacted Technologies

VendorProductVersion(s)CPE
>= 7.3.0, < 7.3.33CPE matchmatch criteria
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
>= 7.4.0, < 7.4.26CPE matchmatch criteria
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
>= 8.0.0, < 8.0.13CPE matchmatch criteria
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:a:netapp:clustered_data_ontap:-:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
25.95%
Probability of exploitation in next 30 days
EPSS Percentile
97.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.2595 is in the 98th percentile among its peer group of 23,701 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

microsoftpatch availablevia msrc
Product: 19641-16823
microsoftpatch availablevia msrc
Product: cbl2 php on CBL Mariner 2.0
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: php:7.4-8070020220707122009.afd00e68
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7Fixed in: rh-php73-php-0:7.3.33-1.el7
View patch

Vendor Advisories (2)

redhatCVE-2021-21707Moderate

php: Special character breaks path in xml parsing

Nov 15, 2021
microsoft2021-Nov/CVE-2021-21707Moderate

Special characters break path parsing in XML functions

Nov 9, 2021

References

bugs.php.net / bug.php
ExploitIssue TrackingPatchRelease NotesVendor Advisory
lists.debian.org / debian-lts-announce/2022/12/msg00030.html
Issue TrackingMailing List
security.netapp.com / advisory/ntap-20211223-0005
Third Party Advisory
debian.org / security/2022/dsa-5082
Third Party Advisory
tenable.com / security/tns-2022-09
PatchRelease NotesThird Party Advisory