CVE-2021-0268Junos OS: J-Web has an Improper Neutralization of CRLF Sequences in its HTTP Headers which allows an attacker to carry out multiple types of attacks.
- 8.8HighCVSS base score
- 0.88%Exploitation in 30 daysEPSS · top 40% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
An Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') weakness in J-web of Juniper Networks Junos OS leads to buffer overflows, segment faults, or other impacts, which allows an attacker to modify the integrity of the device and exfiltration information from the device without authentication. The weakness can be exploited to facilitate cross-site scripting (XSS), cookie manipulation (modifying session cookies, stealing cookies) and more. This weakness can also be exploited by directing a user to a seemingly legitimate link from the affected site. The attacker requires no special access or permissions to the device to carry out such attacks. This issue affects: Juniper Networks Junos OS: 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S5; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R2-S5, 18.4R3-S3; 19.1 versions prior to 19.1R2-S2, 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2, 19.4R3; 20.1 versions prior to 20.1R1-S2, 20.1R2. This issue does not affect Juniper Networks Junos OS versions prior to 18.1R1.
Timeline
ID reserved
By juniper
- 6 months later
· 6 months later
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| juniperCNA (assigner) | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:L |
| NVDNVD · Modified | 3.1 | Critical9.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.88% · top 40% of all CVEs (13 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.8.
Affected products
- unaffected unspecified – < 18.1R1
- affected 18.1 – < 18.1R3-S11
- affected 18.2 – < 18.2R3-S5
- affected 18.3 – < 18.3R2-S4, 18.3R3-S3
- affected 18.4 – < 18.4R2-S5, 18.4R3-S3
- affected 19.1 – < 19.1R2-S2, 19.1R3-S2
- affected 19.2 – < 19.2R1-S5, 19.2R2
- affected 19.3 – < 19.3R3
- affected 19.4 – < 19.4R1-S3, 19.4R2, 19.4R3
- affected 20.1 – < 20.1R1-S2, 20.1R2
What to do
Solution: The following software releases have been updated to resolve this specific issue: 18.1R3-S11, 18.2R3-S5, 18.3R2-S4, 18.3R3-S3, 18.4R2-S5, 18.4R3-S3, 19.1R2-S2, 19.1R3-S2, 19.2R1-S5, 19.2R2, 19.3R3, 19.4R1-S3, 19.4R2, 19.4R3, 20.1R1-S2, 20.1R2, 20.2R1, and all subsequent releases.
Workaround: There are no viable workarounds for this issue other than disabling the J-Web service. To reduce the risk of exploitation utilize common security BCPs to limit the exploitable surface by limiting access to network and device to trusted systems, administrators, networks and hosts.
Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
References
References1
- https://kb.juniper.net/JSA11159 (opens in a new tab)x_refsource_MISCx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-2887 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-0268)Record last updated .