VulnerabilityPublished 17 Mar 2026Updated 19 Mar 2026

CVE-2026-3633: Red Hat Enterprise Linux 10 · CRLF Injection

Affects Red Hat Enterprise Linux 10Source CVE Database V5

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Not known to be exploited · CVSS 3.9 Low.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score

3.9Low

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 14% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: High
User Interaction: Required
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Red Hat Enterprise Linux 10libsoup3	Affected–	Fixed in–
Red Hat Enterprise Linux 6libsoup	Affected–	Fixed in–
Red Hat Enterprise Linux 7libsoup	Affected–	Fixed in–
Red Hat Enterprise Linux 8libsoup	Affected–	Fixed in–
Red Hat Enterprise Linux 9libsoup	Affected–	Fixed in–

AI-suggested

To mitigate CVE-2026-3633, organizations should prioritize applying official patches or updates from Red Hat as soon as they become available. In the interim, developers and system administrators should audit applications and scripts that utilize libsoup's soup_message_new() function, ensuring that the method parameter is strictly validated and sanitized to prevent injection of CRLF sequences. Employing input validation routines that reject or encode CRLF characters can reduce risk. Network-level mitigations include deploying web application firewalls (WAFs) or intrusion detection/prevention systems (IDS/IPS) configured to detect anomalous HTTP request patterns indicative of header injection or request smuggling attempts. Additionally, minimizing the exposure of vulnerable services to untrusted networks and enforcing the principle of least privilege can reduce attack surface. Monitoring logs for unusual HTTP request anomalies and conducting regular security assessments of HTTP client libraries in use will help detect and prevent exploitation attempts. Finally, educating developers about secure handling of HTTP request construction parameters is essential to prevent similar vulnerabilities.

Description

A flaw was found in libsoup. A remote attacker, by controlling the method parameter of the `soup_message_new()` function, could inject arbitrary headers and additional request data. This vulnerability, known as CRLF (Carriage Return Line Feed) injection, occurs because the method value is not properly escaped during request line construction, potentially leading to HTTP request injection.

Impact

The potential impact of CVE-2026-3633 is relatively limited but still significant in certain contexts. Successful exploitation could allow an attacker to manipulate HTTP requests by injecting arbitrary headers and data, potentially enabling HTTP request smuggling or header injection attacks. These attacks could lead to information disclosure, session hijacking, or bypassing security controls that rely on HTTP headers. However, the requirement for high privileges and user interaction reduces the likelihood of widespread exploitation. The vulnerability could affect applications relying on libsoup for HTTP communications, particularly in environments where untrusted input is passed to the method parameter without proper sanitization. Organizations running Red Hat Enterprise Linux 10 in desktop or server roles that utilize libsoup may face risks of degraded confidentiality, integrity, and availability of network communications. While no known exploits exist in the wild, the vulnerability could be leveraged in targeted attacks against sensitive systems, especially in environments with complex HTTP-based workflows or proxy configurations.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Mar 2026, 00:53 UTC

Technical details

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