CVE-2021-21707: Special characters break path parsing in XML functions
Vulnerability summary
CVE-2021-21707 is a medium (CVSS 5.3) vulnerability in debian debian_linux. EPSS estimates a 25.31% chance of exploitation in the next 30 days, higher than 97.9% of scored vulnerabilities. 1 public exploit is recorded.
Not severe (CVSS 5.3, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 17 · Related 13Timeline
- 29-11-2021PublishedVulnerability first disclosed.
- 17-09-2024Last modifiedVulnerability information updated.
Description
In PHP versions 7.3.x below 7.3.33, 7.4.x below 7.4.26 and 8.0.x below 8.0.13, certain XML parsing functions, like simplexml_load_file(), URL-decode the filename passed to them. If that filename contains URL-encoded NUL character, this may cause the function to interpret this as the end of the filename, thus interpreting the filename differently from what the user intended, which may lead it to reading a different file than intended.
CVSS metrics
6 scores · 5 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- OSV · DebianEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- NVDNIST5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- OSV · AlpineEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS trend
Probability
25.31%
Chance of exploitation in the next 30 days
Percentile
98%
Versus all other CVEs
30-day change
Decrease -0.64 pp
From 25.95% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
1 foundExploit Reference (bugs.php.net)
Maturity: unknown
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu4 products
- php5All versions (No fix recorded)
- php7.0< 7.0.33-0ubuntu0.16.04.16+esm3
- php7.2< 7.2.24-0ubuntu0.18.04.11
- php7.4< 7.4.3-4ubuntu2.10
Alpine3 products
- php7< 7.3.33-r0 | < 7.4.26-r0
- php8< 8.0.13-r0
- php81< 8.1.0-r0
Debian2 products
- php7.4< 7.4.28-1+deb11u1
- debian_linuxEOL10.0 | 11.0
Opensuse2 products
- php7&distro=openSUSE Tumbleweed< 7.4.26-1.1
- php8&distro=openSUSE Tumbleweed< 8.0.13-1.1
Suse2 products
- php74&distro=SUSE Linux Enterprise Module for Web and Scripting 12< 7.4.6-1.30.1
- php74&distro=SUSE Linux Enterprise Software Development Kit 12 SP5< 7.4.6-1.30.1
Mageia1 product
- php< 8.0.13-1.mga8
Netapp1 product
Php1 product
- php≥ 7.3.0, < 7.3.33 | ≥ 7.4.0, < 7.4.26 | ≥ 8.0.0, < 8.0.13
Php group1 product
- php≥ 7.3.x, < 7.3.33 | ≥ 7.4.x, < 7.4.26 | ≥ 8.0.X, < 8.0.13
Tenable1 product
- tenable.sc< 5.21.0
10 vendors · 18 products
References
19 links- security.netapp.com/advisory/ntap-20211223-0005/Third Party Advisory
