diff --git a/routers/api/v1/repo/issue_attachment.go b/routers/api/v1/repo/issue_attachment.go
index 6f3e4b5e77..658d18094a 100644
--- a/routers/api/v1/repo/issue_attachment.go
+++ b/routers/api/v1/repo/issue_attachment.go
@@ -15,6 +15,7 @@ import (
 	"code.gitea.io/gitea/modules/web"
 	"code.gitea.io/gitea/services/attachment"
 	"code.gitea.io/gitea/services/context"
+	"code.gitea.io/gitea/services/context/upload"
 	"code.gitea.io/gitea/services/convert"
 	issue_service "code.gitea.io/gitea/services/issue"
 )
@@ -159,6 +160,8 @@ func CreateIssueAttachment(ctx *context.APIContext) {
 	//     "$ref": "#/responses/error"
 	//   "404":
 	//     "$ref": "#/responses/error"
+	//   "422":
+	//     "$ref": "#/responses/validationError"
 	//   "423":
 	//     "$ref": "#/responses/repoArchivedError"
 
@@ -207,7 +210,11 @@ func CreateIssueAttachment(ctx *context.APIContext) {
 		CreatedUnix: issue.UpdatedUnix,
 	})
 	if err != nil {
-		ctx.Error(http.StatusInternalServerError, "UploadAttachment", err)
+		if upload.IsErrFileTypeForbidden(err) {
+			ctx.Error(http.StatusUnprocessableEntity, "", err)
+		} else {
+			ctx.Error(http.StatusInternalServerError, "UploadAttachment", err)
+		}
 		return
 	}
 
diff --git a/routers/api/v1/repo/issue_comment_attachment.go b/routers/api/v1/repo/issue_comment_attachment.go
index 0f8fc96f08..ed8ea10293 100644
--- a/routers/api/v1/repo/issue_comment_attachment.go
+++ b/routers/api/v1/repo/issue_comment_attachment.go
@@ -15,6 +15,7 @@ import (
 	"code.gitea.io/gitea/modules/web"
 	"code.gitea.io/gitea/services/attachment"
 	"code.gitea.io/gitea/services/context"
+	"code.gitea.io/gitea/services/context/upload"
 	"code.gitea.io/gitea/services/convert"
 	issue_service "code.gitea.io/gitea/services/issue"
 )
@@ -156,6 +157,8 @@ func CreateIssueCommentAttachment(ctx *context.APIContext) {
 	//     "$ref": "#/responses/error"
 	//   "404":
 	//     "$ref": "#/responses/error"
+	//   "422":
+	//     "$ref": "#/responses/validationError"
 	//   "423":
 	//     "$ref": "#/responses/repoArchivedError"
 
@@ -209,9 +212,14 @@ func CreateIssueCommentAttachment(ctx *context.APIContext) {
 		CreatedUnix: comment.Issue.UpdatedUnix,
 	})
 	if err != nil {
-		ctx.Error(http.StatusInternalServerError, "UploadAttachment", err)
+		if upload.IsErrFileTypeForbidden(err) {
+			ctx.Error(http.StatusUnprocessableEntity, "", err)
+		} else {
+			ctx.Error(http.StatusInternalServerError, "UploadAttachment", err)
+		}
 		return
 	}
+
 	if err := comment.LoadAttachments(ctx); err != nil {
 		ctx.Error(http.StatusInternalServerError, "LoadAttachments", err)
 		return
diff --git a/templates/swagger/v1_json.tmpl b/templates/swagger/v1_json.tmpl
index 68ae0c3c43..9c78b718a7 100644
--- a/templates/swagger/v1_json.tmpl
+++ b/templates/swagger/v1_json.tmpl
@@ -7606,6 +7606,9 @@
           "404": {
             "$ref": "#/responses/error"
           },
+          "422": {
+            "$ref": "#/responses/validationError"
+          },
           "423": {
             "$ref": "#/responses/repoArchivedError"
           }
@@ -8232,6 +8235,9 @@
           "404": {
             "$ref": "#/responses/error"
           },
+          "422": {
+            "$ref": "#/responses/validationError"
+          },
           "423": {
             "$ref": "#/responses/repoArchivedError"
           }
diff --git a/tests/integration/api_comment_attachment_test.go b/tests/integration/api_comment_attachment_test.go
index d4368d51fe..1b3cae91e2 100644
--- a/tests/integration/api_comment_attachment_test.go
+++ b/tests/integration/api_comment_attachment_test.go
@@ -240,3 +240,31 @@ func TestAPIDeleteCommentAttachment(t *testing.T) {
 
 	unittest.AssertNotExistsBean(t, &repo_model.Attachment{ID: attachment.ID, CommentID: comment.ID})
 }
+
+func TestAPICreateCommentAttachmentWithUnallowedFile(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	comment := unittest.AssertExistsAndLoadBean(t, &issues_model.Comment{ID: 2})
+	issue := unittest.AssertExistsAndLoadBean(t, &issues_model.Issue{ID: comment.IssueID})
+	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: issue.RepoID})
+	repoOwner := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: repo.OwnerID})
+
+	session := loginUser(t, repoOwner.Name)
+	token := getTokenForLoggedInUser(t, session, auth_model.AccessTokenScopeWriteIssue)
+
+	filename := "file.bad"
+	body := &bytes.Buffer{}
+
+	// Setup multi-part.
+	writer := multipart.NewWriter(body)
+	_, err := writer.CreateFormFile("attachment", filename)
+	assert.NoError(t, err)
+	err = writer.Close()
+	assert.NoError(t, err)
+
+	req := NewRequestWithBody(t, "POST", fmt.Sprintf("/api/v1/repos/%s/%s/issues/comments/%d/assets", repoOwner.Name, repo.Name, comment.ID), body).
+		AddTokenAuth(token).
+		SetHeader("Content-Type", writer.FormDataContentType())
+
+	session.MakeRequest(t, req, http.StatusUnprocessableEntity)
+}
diff --git a/tests/integration/api_issue_attachment_test.go b/tests/integration/api_issue_attachment_test.go
index b6a0cca6d5..919dea2e62 100644
--- a/tests/integration/api_issue_attachment_test.go
+++ b/tests/integration/api_issue_attachment_test.go
@@ -173,6 +173,33 @@ func TestAPICreateIssueAttachmentAutoDate(t *testing.T) {
 	})
 }
 
+func TestAPICreateIssueAttachmentWithUnallowedFile(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 1})
+	issue := unittest.AssertExistsAndLoadBean(t, &issues_model.Issue{RepoID: repo.ID})
+	repoOwner := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: repo.OwnerID})
+
+	session := loginUser(t, repoOwner.Name)
+	token := getTokenForLoggedInUser(t, session, auth_model.AccessTokenScopeWriteIssue)
+
+	filename := "file.bad"
+	body := &bytes.Buffer{}
+
+	// Setup multi-part.
+	writer := multipart.NewWriter(body)
+	_, err := writer.CreateFormFile("attachment", filename)
+	assert.NoError(t, err)
+	err = writer.Close()
+	assert.NoError(t, err)
+
+	req := NewRequestWithBody(t, "POST", fmt.Sprintf("/api/v1/repos/%s/%s/issues/%d/assets", repoOwner.Name, repo.Name, issue.Index), body).
+		AddTokenAuth(token)
+	req.Header.Add("Content-Type", writer.FormDataContentType())
+
+	session.MakeRequest(t, req, http.StatusUnprocessableEntity)
+}
+
 func TestAPIEditIssueAttachment(t *testing.T) {
 	defer tests.PrepareTestEnv(t)()